Hitachi EX 120-2 Gremlins

New Member long time lurker. Have a Hitachi EX 120-2 with loss of power and the PVC light is flickering not blinking. Downloaded the Manual from Lachau and tried jumped the 2 and 4 wire on Dr ex.port and don't have the analyzer. The EC blinks (4-5-1) and checked continuity between EC and PVC and tested good according to manual but only get flickering light on PVC . Replaced bad Pilot pump solenoid twice ,second time John Deere part . Inspected PVC internally no smoke or any obvious issue visually same as EC. When machine went down the auto idle power down worked now it doesn't although the light display works. Pump Angle (A)sensor 5 v in center wire changes when rotating by hand.Speed sensor and DP sensor continuity and voltage check out. Pump displacement sensors No.1 and No.2 have no power input key on is this normal?Any idea on why PVC light is flickering? Any way to test PVC without being attached to machine? Thanks in advance.

Welcome to HEF Rash . Rash said: Have a Hitachi EX120-2 with loss of power. Click to expand... Are you referring to a loss of hydraulic power ?, Mostly function speed is slow ? Rash said: Replaced bad Pilot pump solenoid twice ,second time John Deere part . Click to expand... What are you referring to as the pilot pump solenoid ? Rash said: Pump displacement sensors No.1 and No.2 have no power input key on is this normal? Any idea why the PVC light is flickering Click to expand... I have seen some instances where the pump control relay coil is grounded by the PVC only when the engine is running. Do you have 24volts at the #1 and #2 pump displacement solenoids with the engine running ? Check that the PVC and EC ground wire loop terminals are clean and tight where they bolt to the cab floor.

Thanks for the reply Dave. Loss of hydraulic power, overheats quickly, sluggish on all functions tracking,swing boom up down. I replaced the Pump pressure solenoid with JD first one failed. Had rodent damage on wires to pump pressure solenoid and splice it and worked good for years. Had similar system symptoms which was fixed by rewiring and recently had panel off and got bushwhacked by small lodgepole pine . Bought all new wire harness from China which was to short but used it to replace where rodents damaged wire and plug connector . Where does the EC and PVC ground loop bolt to cab floor is it a separate bolt? Don't have any voltage on #1 and #2 pump displacement solenoids and have two new ones which I put on with no change so remounted original back on.Machine is on Mountain no cell service and I will check next trip out. Was reading post about eeprom reset using uv light would this be worth while if grounds check out to reset PVC to reboot and see if the PVC flicker would clear up to get blink function back?

Rash said: Where does the EC and PVC ground loop bolt to cab floor is it a separate bolt? Don't have any voltage on #1 and #2 pump displacement solenoids. Click to expand... The PVC and EC ground wire loop terminals bolt to the cab floor at the bottom leg of the cab heater control panel support. Does the engine stall with any hydraulic function over releif ?

Copy that on ground Dave. Yes it does stall and engine dies. When tracking or using all other functions if you give it to much it dies but if just a little it snails along. Was reading another thread which indicated the Pump displacement solenoid #1 and #2 had their own relays any idea where these are located? Also are these not supposed to have 24 Volts engine off key on?

If you have no power at both pump displacement solenoids with engine running , check for power at terminals #1and #3 at the pump control relay ( power to relay comes from fuse #3 ) . Check if there is power at relay terminal #5 ( to pump displacement solenoids) if not ,temporarily provide a ground at relay terminal #2.. Relay terminal #’s and also Relay location and identification in screenshots below.

Rash said: Also are these not supposed to have 24 Volts engine off key on? Click to expand... It should have 24 volts engine off key on but I have seen some aftermarket PVC’s ground the pump control relay coil only when the engine is running.

Per the service manual if you are getting error code 5 and the auto-idle isn't working, you should replace the PVC and EC. The fact that the PVC light is flickering seems to point to some kind of power supply failing internal to it. I'm not following how you can still read codes if it's flickering.

Thanks Dave, I will try that and report back when I get back to civilization. My PVC appears to be original Hitachi tape part and not aftermarket.

Matt, can't read any codes just the auto idle doesn't function when button is activated and on P after not use for short duration. Was hoping to get flicker light worked out so could use blinks for codes. My fear is if I replace PVC what caused my current issue could fry or takeout new one. Shopping for a Dr ex analyzer any suggestions,if you buy one with palm reader ebay are they out of box ready to go? Thanks for the help. R

There was also a service bulletin regarding the pump control relay coil ground that states, ” There have been some situations where the Pump Control Relay initially energizes, but then loses its ground through the PVC and disengages. When this occurs, the Pump Solenoids do not have voltage applied and the pump stays at maximum displacement. However this can be corrected by rewiring the Pump Control Relay using the following procedure:

1. Cut the Yellow/Green wire connected between PVC connector pin #104 and Pump Control Relay terminal #2. Connect the relay side of the wire to a good ground source.
2. Cut the Blue/White wire connected between Pump Control Relay terminal #1 and the F3 EC Motor fuse (5 amp). Connect the relay side of the wire to a switched fuse (such as F10) so the relay only energizes when the key switch is "ON". “

Rash said: Shopping for a Dr ex analyzer any suggestions,if you buy one with palm reader ebay are they out of box ready to go? Thanks for the help. R Click to expand... . @Chiefdug bought DrEx with a tablet, info below. Chiefdug said: This is his email address. [email protected] I got the Dr.EX from him on Amazon. Click to expand...

If you shorted the Dr EX terminals to have it blink out codes and it blinked 4-5-1, that would indicate error code 5. The 4 is a preamble saying it's the start of the code readout, and the 5, 1 error codes are related to EC-PVC communication. If it's just randomly flickering though and reading out different stuff than is a different story. Is the EC led flashing? Not sure off hand if the pump relay is supposed to be triggered by key-on or engine-start, but I would hope it would be key-on so that the pump angle could be dropped to the lowest possible setting before the engine started. Assuming you already checked fuses to make sure none are blown, relays would be a good thing to check as Dave said. I understand the worry about blowing up a new PVC, I've heard stories of some of the aftermarket harnesses being done wrong. The palm pilot/reader cable works out of the box

Matt yeah it was the EC blinking those sequences. The PVC flicker only and is my understanding codes only come through PVC hence the issue. When I shorted the 2 to 4 on Drex plug it didn't change anything I believe it was red to yellow wires. I did do continuity test from EC to PVC also and all tested ok. Fuses all tested out and have a Couple of new relays.

Update, performed the test Diesel Dave after cleaning ground to cab floor at heater control bracket which looked pretty good. Then back probed the Pump Control Relay had 26.4 V on terminal #1 and terminal #3 and only .3v on terminal #5 while running. When I jump a ground from battery back probed to terminal #2 then I was getting power to solenoid #1 and solenoid #2 in the 23 to 23.3 v . Machine still had same symptoms snail mode/ laboring with the exception when I would boom up and apply stick out it would after few seconds delay do from snail mode to fast function on boom up although still laboring. In the abundance of caution Didn't splice in and cut wires just yet because the wire was black/white out of F3 and and F10 was dummy no power in my fuse panel and wanted to confirm before cutting wires. If I understand Dave's point of this it is to limit to positive power with key on only otherwise it would be engaged at all times? With key on not running I had 23 v on yellow and 1.7 v which goes to solenoid #1 closest to engine and 23 on solenoid #2 23.3V on yellow/black and .2v on red /blue. The angle sensor had 5.1v and adjusted to 4.4 when I twisted and also tested moving which increased in and decreased voltage up and down. The P sensor had 5.1V in and center wire was less maybe by half but i didn't right down by mistake. The PVC still flickering no change. Also the Speed sensor had input 5 V but don't recall other voltage. I Certainly feel progress was made and hopefully this will help us sort out the gremlins.Thanks for all the help thus far it is greatly appreciated R.

If you Backprobe and provide a ground for the pump solenoid furthest from the engine does the hydraulic pump angle sensor output change to less than 1.0 volts ? . The speed sensor located beside the pump angle sensor is only a 2 wire sensor , check it with a voltmeter using the AC scale. Put the 2 voltmeter leads on the speed sensor, the sensor AC voltage should increase as engine speed increases.

Rash said: In the abundance of caution Didn't splice in and cut wires just yet because the wire was black/white out of F3 and and F10 was dummy no power in my fuse panel and wanted to confirm before cutting wires. If I understand Dave's point of this it is to limit to positive power with key on only otherwise it would be engaged at all times? Click to expand... The black/ white wire is correct. Connect it to a “switched” fuse such as the cigarette lighter.

Dave,will change to switched fuse and ground and check speed sensor next trip to the Mountain. Also didn't mention I changed solenoid furthest from engine yesterday with no results but will perform angle sensor test at your direction. Also swapped out relay #8 to EC yesterday after performing tests no change. Thanks R

You can also test the mechanical side of a pump displacement solenoid when off the machine. Put some air pressure into one of the solenoid ports , there should be zero air escaping from the other port.

Will do have dump truck there with air. Just leaving service will report back.Cheers R